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6. Discussion and Conclusions The U.S. chemical industry is the largest in the world, and responsible for a large part of U.S. industrial production (11% of U.S. manufacturing value added). It also consumes approximately 20% of total industrial energy consumption in the U.S. (1994), and contributes in similar proportions to U.S. greenhouse gas emissions. Surprisingly, there is not much information on energy use and energy intensity in the chemical industry available in the public domain. This report provides detailed information on energy use and energy intensity for the major groups of energy-intensive chemical products. Ethylene production is the major product in terms of production volume of the petrochemical industry. The petrochemical industry (SIC 2869) produces an extremely wide variety of products, although most energy is used for a small number of intermediate compounds, of which ethylene is the most important one. Based on a detailed assessment we estimate fuel use for ethylene manufacture at 520 PJ (LHV), excluding feedstock use. Ethylene production is responsible for approximately 34% of energy use in the petrochemical industry. Energy intensity is estimated at 26 GJ/tonne ethylene (LHV), excluding feedstocks. The nitrogenous fertilizer production is also a very energy intensive industry, producing a variety of fertilizers and other nitrogen-compounds. Ammonia is the most important intermediate chemical compound, used as basis for almost all products. In the U.S. ammonia is produced mainly from natural gas. Fuel use is estimated at 268 PJ (excluding feedstocks), while 368 PJ natural gas is used as feedstock.16 Electricity consumption is estimated at 14 PJ. We estimate the energy intensity of ammonia manufacture at 39.3 GJ/tonne (including feedstocks, HHV) and 140 kWh/tonne, resulting in an estimated primary energy consumption of 40.9 GJ/tonne (HHV), equivalent to 36.6 GJ/tonne (LHV). The third most important product from an energy perspective is the production of chlorine and caustic soda. Chlorine is produced through electrolysis of a salt-solution. Chlorine production is main electricity consuming process in the chemical industry, next to oxygen and nitrogen production. We estimate final electricity use at 173 PJ (48 TWh) and fuel use of 38 PJ. Total primary energy consumption is estimated at 526 PJ (including credits for hydrogen export). The energy intensity is estimated at an electricity consumption of 4380 kWh/tonne and fuel consumption of 3.45 GJ/tonne, if all energy use is allocated to chlorine production. Our estimates are based on surveys of individual plants in the industry as well as engineering estimates on the basis of literature values and surveys. This introduces uncertainties in the results. However, we are not able to estimate the magnitude of the uncertainties. Comparison with other official energy consumption statistics is difficult due to the aggregation levels, as well as different sub-sector divisions used in the statistics and this report. Compared to earlier studies (e.g. Brown et al., 1985; Lipinsky and Ingham, 1994) the current report provides a detailed baseline of energy use in these processes, based on a detailed assessment of the industry and technologies used. The report also provides breakdowns for energy use in the various production steps and unit-operations for recent estimates of the energy intensity of processes. 16 Feedstock use in the ammonia industry may result in direct CO2 emissions, in contrast to the petrochemical industry, where most of the carbon in the feedstock is used in the chemical product. 25 1PDF Image | Energy use and energy intensity
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